Generator frequency jumping on 50%+ load 1

[ViCH]

Hi everyone.. Please assist on my brainstorm...
DieselGenset 11kV 50Hz 3.3MVA
It was fully commissioned in 2011 and used for emergency cases and plant Turnaround activities. Working Load was about 1.1-1.2MW (40-45%).. Last year we got some new facilities, and load increased. So we noticed, that on 1.3-1.4MW frequency start jumping from 52 to 47 Hz.. If we add some more load - it trips by underfrequency. Fuel filters are clean, injectors replaced, valves clearness calibrated, electronic governor have no alarms.. on 1.1-1.2Mw frequency stable. It looks like "memory effect"... Any ideas? Please ask if any additional info required..

 

[waross]

UFRO set to 60 Hz.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ViCH]

What do u mean? My location is Asia, 50HZ is normal frequency for us. Underfrequency trip set - 46 Hz, Overfrequency trip- 54 Hz.

 

[waross]

Automatic Voltage Regulator (AVR) setting.
Under Frequency Roll Off (UFRO)
Or probably not.
On an old set it may be the dead-rack adjustment. That is a mechanical stop on the maximum fuel position.
With an electronic governor and an electrically operated fuel control valve it may be stiction in the fuel control valve.
Ultra low sulfur diesel fuel does not always have enough lubricity.
Alternately it may be a dirty fuel control valve.
I had one such fuel control valve give similar problems immediately after the vendors engineers performed "Recommended maintenance".
They flushed the fuel system with a cleaner that removed any lubricity from the valve.
The valve was opened by an proportional electrical signal from the governor.
When the load dropped, the electrical signal would drop but the internal return spring did not have enough force to overcome the stiction.
The valve would stay in the same position and the set would over-speed. Eventually the signal value would drop enough that the valve would move and the speed would drop.
There was a similar problem but to a lessor degree when the load increased. The frequency would drop until the valve "Broke loose" and increased the fuel flow.
I suggest examining the fuel control valve for freedom of operation.
Forgive my first suggestion.
UFRO controls the voltage, not the frequency.
UFRO should start dropping the voltage when the frequency drops below 47 Hz.
Normal operating frequencies are 51.5 Hz at no load dropping to 50 Hz at full load.
With UFRO set to 60 Hz the voltage, as set by the AVR, will start to drop as soon as any load is applied to the set.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

You said 60 Hz again, Bill; you mean 50 Hz, correct?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[ViCH]

yeah waros, I fully agree with You, could be fuel valve. I am not good in mechanical part, so advise me please, if fuel valve have "stiction", so how we can lubricate it after clean?
Regarding frequency - until 45% it working smooth, - without load it stay on 52 Hz, from 1 to 45% - on stable 50 Hz.. Speed and frequency jumps after 45%+, so voltage and currents also jumps with respects to all electrical laws.
The only thing confuse me - our fuel valve is not portion control. Main valve - is OPEN-CLOSE... Fuel valves on cylinders is also solenoid type, so portions are making by pulse. maybe I am wrong.. I will try to clarify with mechanical engineers..

Viktor
Electrical Technician II

 

[catserveng]

It might be more helpful if you could provide more detailed information on the engine you are dealing with, in the size range you are describing it cold be either a medium or high speed engine, you say it has "electronic governor" then describe solenoid operated fuel injection valves, which are typically driven by an ECM type control.

More details on your unit will likely get you better answers.

MikeL.

 

[ViCH]

Diesel Engine: GE 16V228, 1000RPM
Alternator: AVK DIG156I 11kV 50Hz 3375KVA
Governor: Woodward 723plus - is it ECM type?
AVR: DESC2000 (with redundancy)

Viktor
Electrical Technician II

 

[waross]

If you set the UFRO at 60 Hz on a 50 Hz machine....
"With UFRO set to 60 Hz the voltage, as set by the AVR, will start to drop as soon as any load is applied to the 50 Hz set. "(edit)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ViCH]

Bro, forget about 60HZ My location is not USA.. Our frequencies is 50 HZ

Viktor
Electrical Technician II

 

[itsmoked]

LOL! Yes ViCH, he means the commissioned install set the Under-frequency Roll Off for the "other" frequency '60Hz'. The engine runs fine set at 50Hz speed but the voltage regulator could be set to the wrong system causing what you're seeing.

I could see the fuel control solenoid this is the electronic device that manages the engine throttle (NOT the fuel ON/OFF valve) having gummed up over the years at the 1.2MW fuel region. Now while trying to operate at 1.3MW or higher the valve may not be free to move in this area.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I know that your frequency is 50 Hz.
You know that your frequency is 50 Hz.
Everyone here knows that your frequency is 50 Hz,
EXCEPT
The AVR does not know that your frequency is 50 Hz.
You have to tell the AVR what your frequency is.
That is what the AVR jumper is for.
Don't tell me to forget 60 Hz.
Tell the AVR to forget 60 Hz.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ViCH]

Read my top question bro.. This generator commissioned in 2011. It means it was tested with 100% load. All settings at all controllers and relays - 50HZ. So it is not about 60HZ settings. No.

Viktor
Electrical Technician II

 

[ViCH]

itsmoked, thanks, it looks logically right(regarding gumming valve).

Viktor
Electrical Technician II

 

[catserveng]

OK, you have a GE medium speed engine with an electronic fuel injection system. The Woodward 723Plus governor should be feeding a signal to the EFI control module to control fuel rate.

The AVR I'm assuming is actually a Basler DECS200 set up for redundancy, right?

So by your initial description unit appeared to work fine, problems started after increasing site load.

Based on your description could be a mechanical problem, such as limited fuel delivery, a turbo issue, or could just be that the governor dynamics were only setup for the load you had available at the time, and now you may be beyond the programmed dynamics.

You would need to look at the 723 output to the injection control module to start to get an idea where the problem is. Do you have the Woodward handheld or software to connect to the governor?

You should also review the DECS program, it is free from Basler, requires a serial cable normally and has a metering function that lets you see the AVR status and operating modes, also has a datalogging feature that helps in troubleshooting.

My experience on these particular engines is limited, mostly on marine applications. If you can let us know where you are in the world i may be able to point you to a resource for technical help.

Hope that helps, MikeL

 

[ViCH]

My location is Turkmenistan, former Soviet republic. Right side of Caspian Sea.
Thanks for wide answers.. I already found some literarure for setup Woodward governors, and get software for it, and for Basler as well.. As soon I get some results, i will update topic..
Btw.. I also noticed, that lube oil pressure raised since 2011, from 9 bar, to 13 bars... Still no alarms for lube oil, and our mechanicals keep silence.. Filters servicing in time, oil replacement as well, oil analisys result good.. Is it any possibilities of LO high pressure to make problem with unstable speed on high load?

Viktor
Electrical Technician II

 

[RRaghunath]

What is the governor setting - is it droop mode or isochronous mode of operation.
Since your machine seems to be working independent from grid, you need to choose isochronous mode for better speed control.
Hope it works.

 

[ViCH]

AVR mode - load sharing.. Not droop. It is shame for me, but I never heard about isochronous mode.. Regarding governor - I am not sure, need to study software first, to get in and see all parameters..

Viktor
Electrical Technician II

 

[FreddyNurk]

Having the governor set for droop mode is telling, if indeed the set runs at 52Hz no load, but drops to 50Hz as soon as load is applied.


EDMS Australia

 

[waross]

Droop mode is the most forgiving.
No need for isochronous.
I used to have a few dozen customers all on droop mode. They never knew the difference.
Many grids run on 5% droop, but that's another story.

Bill
--------------------
"Why not the best?"
Jimmy Carter